JP6007508B2 - Sound generator using Karman vortex - Google Patents

Description

  The present invention relates to a sound generator using Karman vortices.

  It may be necessary to generate sound waves towards the water. In such a case, a speaker capable of underwater operation formed in consideration of an external pressure and a speaker internal pressure has been used.

  For example, in Patent Document 1, as a part of the outer peripheral surface, a diaphragm of a magnetic speaker is attached in a liquid-tight manner and a drive unit of the magnetic speaker is stored in a liquid-tight manner, and a casing of the diaphragm. An acoustic wave transmitter is disclosed that includes a chamber that is in airtight communication with an internal body space and whose internal volume is variable by external pressure.

JP 2010-57040 A

  However, the sound wave transmitter according to Patent Document 1 has a problem that a drive circuit and a power source are required to make the speaker ring.

  Therefore, a main object of the present invention is to provide an acoustic generator using Karman vortices that does not require a drive circuit or a power source.

  In order to solve the above-described problem, an acoustic generator that is towed by a towed body and emits sound waves includes a vortex generator that generates Karman vortices, a resonance unit that emits sound waves in resonance with vibrations caused by Karman vortices, And a connecting portion for fixing the generating portion to the towing body.

  Since the Karman vortex generated when towing is used as a vibration source, sound waves can be radiated into the water without using a drive circuit or a power source.

It is a top view of the sound generator connected with the towing body concerning a 1st embodiment of the present invention. It is a side view of a sound generator It is a top view of the sound generator which showed Karman vortex typically. It is a perspective view of the resonance part concerning the 2nd Embodiment of this invention. It is a perspective view of the resonance part of other composition concerning a 2nd embodiment.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a top view of a sound generator 2 according to the present embodiment connected to a towing body 3 such as a ship traveling on water, and FIG. 2 is a side view. The sound generating device 2 includes a vortex generating unit 11, a resonance unit 12, and a connecting unit 13 for connecting to the towing body 3. Then, when the towed body 3 tows the sound generator 2, a Karman vortex is generated in the backward direction of the vortex generator 11. The Karman vortex resonates the resonating part 12 and radiates sound waves into the water.

  In the present specification, the traveling direction D of the towed body 3 is referred to as a forward direction, and the direction opposite to the traveling direction is referred to as a backward direction. Moreover, the speed of water viewed from the vortex generator 11 is described as a relative flow velocity. Details will be described below.

  The connecting part 13 connects the vortex generating part 11 and the towing body 3. At this time, if the vortex generator 11 can move in a direction perpendicular to the traveling direction, the Karman vortex is hardly generated. Therefore, the connecting portion 13 connects the vortex generating portion 11 and the towing body 3 in a fixed state so that the relative position of the vortex generating portion 11 with respect to the towing body 3 does not change. That is, the vortex generator 11 moves integrally with the towing body 3.

  The vortex generator 11 is a hollow cylindrical body or a hollow elliptic cylinder. The reason for forming it hollow is to prevent most of the vortex generator 11 from being submerged in water, but not completely submerged. The reason why the cylindrical body or the ellipsoid body is formed is that, for example, in the case of a prismatic body or the like, turbulent flow is likely to occur at the corners, and generation of Karman vortices is suppressed by this turbulent flow. That is, in order to generate Karman vortices efficiently, it is formed in a cylindrical body or an ellipsoid. When the vortex generator 11 is formed of an ellipsoid, the major axis or the minor axis thereof is made to coincide with the connecting line connecting the vortex generator 11 and the towing body 3. This means that the vortex generator 11 is installed so as to have a symmetrical shape with respect to the traveling direction.

  In addition, when the vortex generator 11 is asymmetrical, the force orthogonal to the traveling direction becomes asymmetric across the resonance portion 12, and the connection region between the vortex generator 11 and the connecting portion 13 is twisted, This is to prevent the connection region between the vortex generator 11 and the connection part 13 from being damaged.

  The Reynolds number varies depending on the size of the vortex generator 11 (for example, the diameter in the case of a cylindrical body), the density of water, the relative flow velocity, and the like. When the Reynolds number is about 50 or more, Karman vortices are generated. Note that twin vortices are generated when the Reynolds number is about 50 or less, and turbulence is generated when the Reynolds number exceeds about 1500. Further, the relative flow velocity can be generally regarded as the speed of the towing body 3.

  Therefore, a standard speed of the towed body 3 is set, and the size of the vortex generator 11 is determined so that the Reynolds number is about 50 or more with this speed as a relative flow velocity. Note that when the relative speed changes due to wind or tidal current, the Karman vortex is constantly generated by adjusting the speed of the towed body 3.

  The resonating part 12 is formed by a plate-like member and is connected to the vortex generating part 11. At this time, the resonating unit 12 may have a configuration in which the relative position changes with respect to the vortex generator 11. That is, the vortex generating part 11 and the resonating part 12 may be connected by a link structure.

  Such a resonating portion 12 vibrates due to a force received from a Karman vortex generated in water. FIG. 3 is a top view of the sound generator 2 schematically showing the Karman vortex 14. The Karman vortex 14 is generated in the rearward direction of the vortex generator 11 along the traveling direction (along the wake of the vortex generator 11) and alternately. And the resonance part 12 vibrates by the Karman vortex 14. The resonating unit 12 resonates with the vibration of the Karman vortex 14 and radiates sound waves into the water.

  If the radiated sound wave has a large sound pressure, the sound wave reaches deep propulsion. In this way, when it is desired to make the sound wave reach a deeply propelled place, the weight of the resonating unit 12 needs to be heavy. From such a viewpoint, the resonating part 12 in the present embodiment is formed of a metal such as iron or stainless steel. However, because metal is heavier than water, it may sink. In such a case, a float or the like is attached.

  As described above, when the sound generator is towed by the towed body, the resonance unit resonates and radiates sound waves into the water, so that the sound waves can be radiated into the water with a simple configuration without using a drive circuit or the like. Is possible.

In addition, in the said description, although the case where one vortex generation | occurrence | production part and one resonance part were each provided is shown, you may provide these two and arrange in series or parallel. By providing a plurality of vortex generators and resonating parts in this way, the sound pressure can be increased.
<Second Embodiment>
Next, a second embodiment of the present invention will be described. In addition, about the same structure as 1st Embodiment, description is abbreviate | omitted suitably using the same code | symbol.

  In the first embodiment, the resonance unit 12 is a plate-like member. In contrast, in the present embodiment, a hollow rectangular body is used. At this time, if a large resistance is generated at the end face of the resonating unit 12, the water flow is disturbed by the resistance, and the Karman vortex may not be easily generated. Therefore, the end face of the resonating unit 12 according to the present embodiment is formed in a streamline shape.

  By making the resonance part 12 into a hollow rectangular body, since the hollow space functions as a resonance box, it is possible to radiate a sound wave having a large sound pressure.

  At this time, for example, as shown in FIG. 4, if water W or the like is stored in the internal space S of the resonance unit 12 and the water level can be changed, the resonance frequency can be changed. . That is, a sound wave having a desired frequency can be emitted.

  Further, as shown in FIG. 5, the internal space may be partitioned into a plurality of spaces by partition plates, and the water level stored in each space may be changed. In this case, since resonance occurs in each partition space, it becomes possible to radiate sound waves having a plurality of frequencies.

2 Sound generator 3 Towing body 11 Vortex generator 12 Resonant unit 13 Connection unit 14 Karman vortex

Claims (6)

A sound generator that is towed by a towed body and emits sound waves,
A vortex generator that generates Karman vortices;
Resonating with vibrations due to the Karman vortex and emitting sound waves;
A sound generating device comprising: a connecting portion that fixes the vortex generating portion to the towing body. The sound generator according to claim 1,
An acoustic generator comprising a plurality of at least one of the vortex generator and the resonance unit. The sound generator according to claim 1 or 2,
The acoustic generator according to claim 1, wherein the resonance part is a hollow body. The sound generator according to any one of claims 1 to 3,
An acoustic generator according to claim 1, wherein water can be stored in the resonating portion and the water level can be adjusted. The sound generator according to any one of claims 1 to 4,
The sound generator according to claim 1, wherein the vortex generator has a cylindrical or ellipsoidal horizontal cross-sectional shape. The sound generator according to any one of claims 1 to 5,
The acoustic generator is characterized in that the tip of the resonance part is formed in a streamlined manner.

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